Concentration of comminuted materials



y 1960 c. A. HOLLINGSWORTH ET AL 2,938,629

CONCENTRATION OF COMMINUTED MATERIALS Filed. July 28, 1955 3Sheets-Sheet 1 INVENTORS Clinron A. Hoilingsworrh BY Charles J M DonoATTORNEYS May 31, 1960 c. A. HOLLINGSWORTH ETAL 2,938,629

' CONCENTRATION OF CQMMINUTED MATERIALS Filed July 2a, 1955 sSheets-Sheet 2 INVENTORS giijinfon AljHollin sworrh. BY or es c on M,MA

ATTORNEYS May 31, 1960 c. A. HOLLINGSWORTH ET AL 2,938,629

CONCENTRATION o? COMMINUTED MATERIALS Filed July 28, 1955 I 3Sheets-Sheet 5 INVENTORS Clinion A. Hollingsworrh BY Charles J. McDonald 1 Gmammnamrsmz ATTORNEYS United States Patent G CONCENTRATION OFCOMMINUTED MATERIALS Clinton A. Holiingsworth, Lakeland, and Charles J.

McDonald, Plant City, Fia., assignors to Smith-Douglass Company,Incorporated, Norfolk, Va., a corporation of Virginia Filed July 28,1955, Ser. No. 525,051

3 Claims. (Cl. 209-170) This invention relates to the concentration ofcomminuted materials by pneumatic flotation, and while particularlydescribed with reference to the concentration of minerals, it may beadvantageously applied to the flotation treatment of various othermaterials, such as graphite ores, coal, mineral slimes, sewage, tradewastes, chemicals such as starch-gluten mixtures, water solublematerials etc. More particularly, the invention involves an improvedmethod of aerating a reagentized (or non-reagentized) pulp of mineral(or non-mineral) by introducing (into a body of the pulp) watercontaining entrained air in an extremely finely divided state and undersuch pressure as to exert a force against and throughout the pulp bodysuificient to keep the pulp in motion at all times.

One object of the invention is to provide an apparatus which is simplein construction, low in cost of manufacture, highly eflicient inoperation and low in cost of maintenance, requiring no outside powerconsumption for its operation beyond the normal water volume undernormal pressure required for the operation of the flotation process byother methods. The apparatus contains no moving parts and does notrequire a source of compressed air or blower air since it obtains therequired air from the surrounding atmosphere at normal atmosphericpressure.

Apparatus (commonly called flotation machines or cells) in common use atthe present time require considerable mechanical energy to maintain aflow of solids through the cell or system of cells. This is generallyachieved by the use of rapidly moving agitators which tend to keep thesolid particles in suspension thus permitting the flow of water to carrythe solids through the cell. At the same timethe air, required toperform the flotation action of the reagentized solid particles, iseither introduced under pressure, or is drawn in through a hollow shaftof the agitator, or is drawn in by the agitator through a pipeterminating just under the impeller or agitator of the cell. In othercases where no agitator or impeller is used, air is forced into theapparatus along the center of the cell close to the bottom and undersome pressure from a high speed blower to maintain the solids insuspension while again the water passing through the cell keeps thesuspended solids moving therethrough. In still other types of apparatusair under pressure is introduced through a porous medium at the bottomof the cell and its expulsion through the porous medium keeps themineral pulp suspended while water introduced above the porous mediummoves the suspended solids through the cell.

In all these apparatus the air is introduced by means of mechanicalaction and expended electrical energy and under such violent agitativeaction as to produce undesirable turbulence in the cell unless movementof the pulp in the cell is quieted down by the use of weirs, bafiies"tee or grids of one kind or another. In the agitator type apparatus theagitation is generally so violent as to cause considerabledisintegration of the solid particles, thus producing undesirablenear-colloidal material generally referred to as slimes.

There are several reasons for avoiding the formation of slimes. Forexample, in the beneficiation of Florida phosphate ore the phosphaticvalues in the slimes run from 20% BPL (bone phosphate of lime) to 35%BPL and at the present time recovery of these values from slimes has notbeen economically achieved. Formation of these phosphatic slimes byexcessive agitation reduces not only the recovery of phosphate valuesbut is responsible for economic losses as well. As is well recognized inthe industry, slimes seriously affect the amount of collector'reagentsrequired to produce good metallurgy. This is even more true in the caseof cationic flotation where the collector reagent can be completelyinactivated by the presence of slimes. Another point of great importanceis the fact that since phosphatic slimes rarely settle beyond 15%solids, huge areas are required to settle out the plant waterscontaining them and these areas filled with the phosphatic slimes are atpresent waste land since they cannot be used for any purpose. Therefore,the elimination of any small percentage of phosphatic slimes in theflotation process advantageously increases the volume of material whichdoes not require storage for a useless purpose. Similar problems arepresent in the case of almost every flotation operation.

In the conventional present-day methods of flotation the production ofslime causes considerable interference in the proper execution of theflotation process. Slimes also result in an appreciable consumption ofcostly reagents, or the use of additional reagents to prevent theirinterference, or to keep the slimes under control. In the presentinvention the agitation action of the combined air and water is of sucha gentle nature as to prevent excessive sliming of the solids (Whethermineral or gangue) during the process of flotation. This is particularlytrue when a cationic reagent isused as the collector since cationicreagents are in most cases quite sensitive to slime and do not performwith eificiency where slimes are rapidly created during the retention ofthe comminuted solids in the cell.

All previous attempts to use only air andwater as prime movers of solidsthrough a flotation cell (without recourse to agitators or impellersactivated by mechanical means) has necessitated the consumption ofconsiderable power in order to introduce the required air at a pressureequal to or greater than the hydrostatic water pressure within the cell,or at least sufiiciently great to exert a force which will keep thesolids in suspension while the flow of water moves these solids throughthe cell. A

Not too much attention has heretofore been directed to the actual sizeof the air bubbles introduced into the apparatus. In most cases theseare relatively large, while in others their size depends on the poreopening of the porous material through which the air is forced. Wherethe impeller acts as the suction force to pull in the air, the air canbe beaten to a relatively small bubble by the action of the impeller.

In none of these heretofore common methods of aeratlon does all thewater present contain entrained air. It is also apparent that where airis forced into the apparatus under pressure the air bubbles arerelatively large and consequently the total surface area of theentrained air bubbles in the apparatus is relatively small. This totalsurface area of the entrained air bubbles increases as the air bubblesize decreases. It is recognized in the art that without, air noflotation can take place, and the efiiciency of. the flotationprocess:depenclsw upon the. air volume, increasing as the latterincreases. Flotation research has shown that the process is madepossible by the attachment of air bubbles; to the solid particle to befloated. Therefore the smaller these bubbles are the rnore of ,j'themcan attach' the'riijs'elves to the selectiyely re agent tied particle"to be floated resulting in aimoreef fici ent float with less air:andi'less effort? llilordeifto do this fan'efficienfmeans'of producingdiminutive air bubbles is re quired,.and such air bubblesmusflbecompletely dispersed or eiitrainedjin the water or'other liquidjnwhichthe'yfunctionfastcfiriersl i great advantage or are raven on isihfth eiOllglg/ lliqllefl mer t within the" apparatus is p o'd ced by theliqu d wh ch is n' rmally introduced'as thecarr'ie or vehicle for theqcost is'jthereby fefiected' since no power is required eitherforfabloweij to pro cfe air orfor the motors necessary to turn the;convent onal impellers. Only 'the amount of liquid iordiharilyrequiredto ,out'the; flotation proc-l: ess'is utilized to provide allthe necessary force to 1ntroduce the finelydivf ed a'ir'a's well as'ftomove the pulp through the apparatus and carry the miner'alizedair'bubblesto the" surface' in 'a froth and out ofgthe; il' par atu sint'o the froth discharge launder's,

In" orderjto maint'ain 'pro'perf'level of the water (or other liquid) inthfe'japparat'us, aerated Much-aerated make up'water (or liquid) maybebled-in Without afiecfi ing' the efiiciency of the process," l

In the pre's'ent invention nolimitation is placed on the physical shape,or dimensions of the appa'r" us in which the liquid aerator operates;"On the contraryj'the novel liquid aeratofot the invention performs"equnly,

well in a shallowitank type cell or 'ih a'narrow' deep cell: wherethe'internal pressure to be'ove'rcome'by the aerated V liquid is-twddrthreeumesme'press rebf a shallow inedlin'the" e rh psl d e-l thin the.cell is cell. The air is so welldisf r's liquid thaff it doe'sjnotjsegrat pendent on the fac't'that all 'the liquid" Asf'lready ointed out, thesize, ,shape and. general dimensions of the flotation cell dopotafiecttheefliciencyt moving"th'e irothfproductf of operation ofthecell equipped with .the, novel liquid 'aera tgrs of the invention, 7These haye shown themselves to be n, y'..y',ve11j' adhered, to .a.Shallow .tanletype cell .in which l discharge of froth takes place,. orin a type cellin Whichthe aeratedmineral particles suited is of urse depe'nden t on the nature of themineral or other mater lbeirig W ear t rgatethess lp .c stw th ocessed .With some materials...

mechanical agitation in addition to liquid aerators. It may also be.advantageous in some.operationsatooperate one or more cells of amultiple cell bank with liquid aerators and one or more cells withagitators, as, for example, where metallic type ores are treated whichhave a high specific gravity and are difficult to keep in suspension.Again it may be found advantageous to operate a bank of cells usingliquid aerators in the first group of cellswithout agitators in;theremo,val of -easily slimed materials and follow this with the secondgroup of cells in which both aerators and agitators are employed for theresidual float. I

In the generalconstructionoj theflotation apparatus, the location of theliquid aerators is not critical'. The

; aerators may be positioned above the cell with long dischargepipesleadinginto.the lower strataof pulp in the cell. They mayextendthrough the sides of the cell to discharge directly into thepulp-area, or they may be located on the bottom of the cell to dischargeupwardly intov the .cell. Neither .,is the angle of .insertion of theaerators critical, andpthey may begpla I to they cell wall s orat suchanangleltheretias to provide. e greatest h u t: in hepul it in he n. ePe -l tive of the, actual locatiojaoi e liquid aeftprs they.. arearranged to introducelaerate li quid; into{a longitun, dinallyflowingtbody rmine "i thpbottonioffthe flotation 4 ubstantially lessthan; half thejc'ells 'depthland'over, stantially. th.:entire.transverse area of the pulp -body :at .the .depth of la'eratedf. liquidintroductiori v M L i l The liqui'cl'"'a'erators constitutemg es sentially noyela;

featurehof thefinventi characte ed by.,. unique;andefficientllaerating,action; The aera e] are. adapted to completelyaerate each particle of liquid how-I, ing through them, and ,the liquidand air. in intim te union. enter thecelllas a; jet streaf a j, sipatedby a difiusion plate;or ,pthe1i suitable means;of spreading theresulting jet through the cell In alpreferred form of the aerator,liquidhtefgh waten) passing through a constriction tube ('som ewhatllike ga venturii.

tube) produces a suction of such niagnitude as to draw,..

in sufiicient air to completely aerate gen the liquid in creating suchsuction and also sufiicient'air. toperform the aeration of thecommiii'uted.particles.,tolbe floated The volumeof air'injected ihto'theliquid stream-is de;. pendent on the anglepfthe liquicl enterl tion zo ne.f Itis within thi zo e that the actualiihdgeu ii magent and id, eeplae endij h ams. completely' dispers 'ed in'jth liqu all af l i r innethen ei If e the apparatns' orth jtailingsdlsc erg h quidaeien m b meetterials depending ontheps l or the choice i oi? thegmanu operation inwhich c'orrosive act1 n' existsg they ".bej made of plastic, hardrubbeiyKarbaitje, graphitejpr-QStill-Q less steel. Brass, copper, blackiron or other mach inable metals or-non-metals may be used intheirinanufaclture The aerators where used. in non-corrosive operations.may be machined from one metal and then .platedwith another, or theparts thereof may be made from different metals if required or desirediIn processes where a liquid other than water is used,

the aerators perform equally-well.- Some procesees par- .ticularlythosexin the potash,--andlother soluble-mineral salt field, useasaturated solution" (brine) 'of the water;

soluble mineral .salt which is to be concentrated, ias the vehicleofvthefprocessr This-saturatedebrinefwhen used in place of water,aeratesandentrains -finely-dispersed air as completely as does water.Processes carried out in' non-aqueous liquids can utilize the inventionto a dis-; tinct advantage since. the sameliquid can'be'usedover andover again to draw in additionalairin the consumation of the flotation.operation.

h1ch may be. dis- Onev of theimportant advantages-of the invention isremoved from a flotation cell while the cell is operating, withoutmaterially afiecting the operation in any way. The removal of individualaerators may become necessary at times to permit cleaning orreplacement.

The invention may advantageously be embodied and practiced in aflotation cell having upright side walls and a solid bottom, say about 4x 4 ft. square with the side walls about 4 ft. in height, equipped witha feed intake at one end and at the other end with a tailings dischargeor else joined to a similar cell, or bank of cells, the last one ofwhich is equipped with a tailings discharge valve, gate, or the like.Through such a cell (or bank of cells) the body of mineral pulpundergoing pneumatic flotation flows longitudinally from the feed inletto the final tailings discharge. At the top, the side walls of each cellare provided with froth discharge lips or weirs which are so constructedas to control the height of the liquid level in the cell. Near thebottom of the side walls, say about 3 inches from the bottom, there arewelded through the wall of the cell a plurality of pipe sleeves. In acell having perpendicular side walls, these sleeves are fitted on theinside of the cell alternately with 4 inch and 8 inch long nipples,which in turn are equipped with a butterfly or similar type of checkvalve into which another short discharge nozzle is fitted whichpreferably is of such form that the aerated liquid is dischargedtherefrom as a flat jet spreading over a substantial transverse area ofthe cell at the depth of aerated liquid introduction. the cell wall isfitted the liquid aerator which is in turn connected through a valve tothe main liquid header pipe.

In cells of the type in which the bottom is only from 12 to 18 incheswide and the side walls flare outwardly to around 48 inches wide at thetop, a similar plurality of pipe sleeves are welded into the cell walls.However, in this type of cell it is preferred to position the checkvalve outside the cell walls leaving within the cell only the dischargenozzle.

The aerator may be of any air-injector type suited for the purpose. Awell-known type is that used in the laboratory as a filter pump oraspirator, which operates by the entrainment of air in an injectedstream of water. This type is not well adapted for commercial sizeflotation cells since the air intake is relatively small and a verylarge number of units are required to give satisfactory performance.However, this type of air-injector has worked satisfactorily inexperimental size or laboratory flotation cells where the air and liquidrequirements are comparatively low.

We have discovered that a similar effect can be achieved (in which theair volume is relatively large) by passing a jet of rapidly movingliquid into an elongated tube provided with an air intake approximatelyat the outlet of the jet of liquid. Although in its preferred form thistube has a constricted area toward its outlet end, good performance hasbeen obtained with a tube having a bore of uniform diameter. However, inthe latter case slightly less air is drawn in by the same volume ofliquid passing the air intake.

The invention will be better understood from the following descriptiontaken in conjunction with the accompanying drawings, in which:

Fig. l is a plan, partly in section, of a fluid aerator embodying theprinciples of the invention,

Fig. 2 is a sectional elevation of a lower corner of a flotationapparatus with a fluid aerator unit extending through a side wall,

Fig. 3 is a detail view of the flared end of the aerator unitsdischarge, nozzle.

Figs. 4 and 5 are a transverse sectional elevation and top plan,respectively, of a flotation apparatus embodying the invention, and

Into the outside opening of each pipe sleeve in l Fig. 6 is a transversesectional elevation of a slightly modified form of apparatus.

The liquid aerator comprises a liquid spray nozzle 10 having a taperedor jet discharge end 11, and an internally threaded coupling 12 at itsother end. A pipe 13, in which is operatively included a value 14,connects the coupling 12 of the nozzle 10 to a source of water or' otherliquid 14' under a pressure normally ranging from about 15 to about 60pounds per square inch.

One end of an elongated tube 15 is screw-threaded onto the discharge end11 of the nozzle 10. The tube 15 has one or more air inlet vents oropenings 16 positioned slightly back of the discharge end of the nozzle.Preferably, the elongated bore of the tube 15 is constricted toward itsdischarge end to provide increased efliciency of air intake. The otherend of the tube 15 is screwthreaded (preferably by standard pipethreads) into a pipe sleeve 17 secured by welding or the like in theupright side wall 18 of a flotation apparatus. Inside the apparatus, anipple 19, to which is attached a butterfly check valve 20, connects thepipe sleeve 17 to a discharge nozzle 21. The outlet of the nozzle 21 isof fishtail configuration, i.e. elongated or spread horizontally, asbest shown in Fig. 3, in order to spread the aerated liquid over asubstantial transverse area of the pulp body in the flotation apparatus.Aeration takes place within the elongated tube 15 and the aerated liquidemerges from the discharge nozzle 21 under considerable thrust.

The jet stream of liquid discharging from the nozzle 10 draws inatmospheric air through the vent or vents 16, and the draw-in air isintimately mixed with and thoroughly disseminated throughout the liquidstream in the bore or chamber of the tube 15. The thus-aerated liquidpasses into the nipple 19 through the check valve 20 and dischargesfan-wise from the nozzle 21 into the body of mineral pulp in theflotation apparatus.

Figs. 4 and 5 diagrammatically illustrate a complete flotation cellembodying the invention. The liquid aerator units of the constructionshown in Figs. 1, 2 and 3, extend inwardly through each side wall 18 ofthe cell, with alternate discharge nozzles 21 extending further into thecell than the other adjacent nozzles. Thus with a cell width of about 4feet the alternate nipples 19 may advantageously be about 4 and 8 incheslong, respectively. The cell has a feed intake launder 22 at its forwardend and a tailings discharge launder 23 at its opposite end. The upperportions of the side walls 18 flare outwardly and terminate at theirupper edges in froth overflow lips 24 discharging into suitable frothlaunders (not shown). Each cell unit may be a separate structure, withthe discharge from one cell constituting the feed of the next cell in abank or series of cells. Or, as shown in Fig. 5, several cells may beformed in an elongated structure or tank by one or more verticalpartitions 25. The partitions 25 are provided with suitable openings topermit the discharge of pulp from each succeeding cell to the followingcell in the bank.

In the form of cell shown in Fig. 6, the side walls 18' slope downwardlyand inwardly to a relatively narrow bottom 26. Only the sleeve 17'(welded in the wall 18) and the discharge nozzle 21 (screw-threaded intothe sleeve) are positioned within the cell, the check valve 20 beingscrew-threaded onto the elongated tube 15 and positioned outside thecell between the sleeve 17' and the tube 15.

In some operations it may be desirable to diminish the amount of aeratedliquid introduced into the flotation apparatus. This may be accomplishedby appropriately adjusting the valves 14 of the fluid aerator units topermit introduction of the desired volume of aerated liquid, and thenadding unaerated liquid into the feed launder 22 through a valved supplypipe 27. The liquid supply pipe 27 also permits adjusting the liquidlevels in a series of cells to the proper heights for optimum operation.

The following examples illustrate various advantages of the invention.

7 a p e .1

The tests of this example oompare the attrition losses' of an :aerated:liquid flotation cell of the -invention with thoserof aconventionabcell of the agitator type.-:

An aqueous slurry from the second cell of a'simcellbank=ina -cationicflotation process employingan amine as the -collector-agent wascollected and screened to remove all plus l50 mesh particles; Theresulta'nt' slurrywas then mixed-toassure complete and uniformdistribution of solids in the waterand 1000 ml-nwerepoured into agraduated cylinder; The-sameprocedure-wasfollowed with each typeofcel-l.- The cylinder-contents were-al lowed to settle forl5 minutes atwhich-time the volume-ofz settled solids was determined andexpressed;in-percentaon theoriginal yoluineof slurry (IOOO-ml.)

1 ST .N 1

"Percent Pe'rcent TYPE/Cell Volume :BRL inn:

Settled; dry Solids Solids V AeratedLiquid can; v 0.2 45.52; Agitator.Cellt. f a 0.84 l. 56. 07.:1.

'25: TEST No. 2

Percent Percent TypeCeIl Voluine Q BPIrin Settled dry Solids SolidsAerated'Liquid' Cell 0. 1 44:36 Agitator Cell r 1.0 48.16 1

In both-these tests the aerated liquid cell 'consistedof' 5 a battery.of six cells the first two of which were equipped with liquid aeratingunits of the inventionwhilethe re A mainder were cells of theagitator'type. The agitator cell' on the other hand was a six cell bankcompletely equipped with mechanicaljagitators but with no liquidaerators. 0 The slurry specimens were taken at the juncture of-thesecond and third cells but in the second cell inorder to give a goodcomparison of the actions of the aerated liquid cell'and the agitatorcell. These tests show that attrition losses are practically negligiblein the aerated liquid cell in comparison-with such losses in theagitator cell.

TEsT NO. -s

Tests 3 andgl illustrate the difference in.attrition.losses:.r wbetween. the .aforesaid two types. of cells when an anionic 150flotation .operationsis. carried. out ;on. phosphate ore. 1 The; slurrysample was .taken.at the end of .thetcellinrthe tail ingsv dischargelaunders.

Percent 55 Example II h i tfi- V- i am le itrate th d 's asei inz psoluble obtained using a 6-cell combination Qf QVQ aerated 1:75 a;

a; liquid cells andiour-agitator cells andacompering these:resultsgwithga. g6-cellaagitator bank inea cationic flotation? operation(cleaner circuit) carried, out (on phosphate ore-.1-

' TEST N O; 1.

Conc.-; Feedz.

V .Tsils, Type Cell 1 Percent Percent Percent Percent Percent rBPL' BPL-Iusoh BPL Insol Aerated Liquid Cell; 76.94. 2. 54 73. 6.40 18.38Agitator Cell 76541 3. 40 "7330* 6.40 21.68-

TESTNOJ Conch, Feed... Tails?- Type.-Cell::- a 1. Percent 1 Perc ntPercent Percent Percent BPL BPIT' Insol BPL" lrlsol Aerated Liquid oeu76578" 0. 27 73.53 7.40 1 17.22 Agitator C9114--. 75. 82" 3..06= 7173.53 7. 40 l 19.99' i TES'DNO; 3.

Cone Feedr', u .Tai Y Typgfigllg: 1 Percent Percent Percent PercentPercent BPL,

BPli' Insol BPL" 111501 Aerated 'Liquid Cell: 14.7 2.60 71941 7.4414:62- Agitator Cell.': 7 '75;32.: j 3. 641. 71:41 1 1.44 19. 56

In each of these tests the. aerated, liquid-cell of the -iinvention:producediunder;identical conditions a much lowerinsjoluble in' theconcentrate-,andQa muchflower, tailing content of,BPL.i The. feedinthsetestslwas a J rougher concentrate] product from p a primary fattyacidif caustic-fueljoil flotation step which fwas deoiled withisulei 4phuric acidand' agitation rinses prior to introduction as..-

are the subject of the inyentiom,

Example llf The followingtestsrcornpare the effectiveness--of-'"theaerated liquid cell and the agitator cell 'in -a single' cell'*equipp'ed with both 'liquid aerators 'and agitators; In

two of the tests only the liquid aerators were functioning i and noagitators were running; while in the other test only. the agitators".were running in a conventionaleflotation .operatio'nabut.nos-liquidaerators' were operating; 'The largeimpeller runner. inlthecell interferedsomewhat:' with the circulationpofthe pulp'and the..operation ;of the aerated liquid cell;v ,since this :runner': is1.:not; normally present in an operating'aerated liquid-cells:Eveneunder these adverseconditions the aerated liquidcell performed as;well as :the agitatorv cell with :whose; operationzther liquid aeratorsdo not interfere. These tests werejrunjon raw phosphate, ore .feed.jcoming into .theiflotationsection; and employed: a fatty;acidcaustic,-fuel .oil. mixture :38 the flotation reagent withremovakof a phosphate froth- "while discharginga silica tailing.

Cone.

Tallsy: 1 J Test No. Percent CellOp'efating With Percent Percent BPL BPLInsole .30 12.13 Liquid Aerators 011157,. .50 11. 30- Agitators only.":g- 7.08. L1quid Ae1-aters$nly.

9 Example IV The tests'oi this example were run with a primary (rougher)step feed similar to that of Example III. In these tests, two-cell bankswere used, one being completely equipped with liquid aerators and noagitators and the other being completely equipped with agitators and noliquid aerators.

In this rougher step float, as in a cleaner step float (Example 11), theaerated liquid cell produces a concentrate of lower insoluble contentthan the agitator cell.

Example V In this example, rougher step floats of a raw phosphate orefeed were carried out in a combination cell and in an aerated liquidcell. The combination cell comprised a six-cell bank of which the firsttwo cells were equipped with liquid aerators while the last four wereequipped with conventional agitators. The aerated liquid cell was asix-cell bank completely equipped with liquid aerators and having noagitators.

Cone.

Tails, Percent BPL Type Cell Percent Percent BPL Insol Aerated LiquidCell Combination Cell com Example V] In this example anionic flotationof the same phosphate ore feed was carried out in an aerated liquid celland in an agitation cell. The aerated liquid cell gave lower insolubleand higher grade of concentrate under substantially identical conditionsof operation.

Cone.

Tails, Type Cell Percent Percent Percent BPL BPL Insol Aerated LiquidCell 74. 36 5. 50 18. 92 Agitator Cell 71. 41 7.26 14. 75

The invention may be efliciently carried out in a single cell or in anymultiple cell system with equally good results. Any number of liquidaerators may be installed in one cell. It is possible in a small cell toeffect flotation separation with but one aerator, while in a larger cellthe required number may be many times that.

In cationic flotation where no pre-conditioning is re quired, it may bedesirable to utilize one or more of the aeration units as reagentdispersion units in which case the reagent is allowed to feed into theair vent in place of a part or all of the air volume, thus givinginstantaneous dispersion when the mixture enters the cell.

It may also be desirable to aerate with a gas other than.

atmospheric air, in which case the gas supply is connected to the airvent and the apparatus operated as with atmospheric air. 7

Where a soluble ore is to be floated, a saturated solution of the ore inwater is pumped through the liquid nozzle 10 and also to the make-upliquid supply pipe 27. Similarly, where flotation is carried out in anon-aqueous liquid (i.e. other than water or a soluble ore solution) thenon-aqueous liquid is pumped to they liquid nozzle 16 and, whererequired, to the supply pipe 27.

The invention may be practiced with advantage in any type of flotationoperation, whether the floated fraction is the desired value or thefloated fraction is the waste or gangue material. The floated fraction,whether value or waste, depends on the type of material undergoingtreatment, and (where required) on the reagents used to promote thefloat. In the interest of simplicity, mineral in the appended claimsincludes any comminuted material as hereinbefore explained, the mineralfroth may consist essentially of either the desired value or the wasteas hereinabove explained, and the residual demineralized pulp is theoriginal mineral pulp from which a substantial amount of either thedesired value or the waste (as the case may be) has been removed in themineral froth.

In practicing the invention, the density of the mineral pulp feed to thecell (e.g. to the feed intake launder 22 of Fig. 5) is higher than itwould normally be in conventional agitator or pneumatic types of cell.The amount of liquid (as aerated liquid) which is introduced into themineral pulp through the liquid aerators generally ranges between 20 and70% of the total liquid of the pulp; the usual amount being about 50%.If it were practical to use a dry feed to the cell, all of the liquidrequired for pulp-making could be introduced as aerated liquid. Thetailings or residual demineralized pulp discharged from the cell (e.g.through the tailings discharge launder 23 of Fig. 5) is accordinglysubstantially more dilute than the mineral pulp feed to the cell.

We claim:

1. A pneumatic flotation apparatus comprising the combination with atank adapted to contain a longitudinally flowing body of mineral pulpand having mineral feeding means and pulp discharge means at itsopposite longitudinal ends respectively, of a multiplicity of liquidaerators positioned outside the tank each of which includes a liquid jetnozzle and associated means for drawing atmospheric air into the aeratorby suction created by the liquid jet discharged from the nozzle and anassociated tubular chamber in which the drawn-in air is adapted to bethoroughly disseminated throughout the liquid discharged from thenozzle, means positioned in proximity to the bottom of the tank forintroducing aerated liquid into the tank in a substantially horizontalplane and over substantially the entire horizontal area of the tankproximate that plane, said means comprising a series of conduitsextending into the tank from at least one side wall thereof and havingdischarge openings at their inner ends, the discharge openings oi saidseries of conduits being located alternately at different distances fromsaid side wall, and tubular means for operatively connecting saidtubular chamber to said means within the tank for introducing aeratedliquid.

2. A pneumatic flotation apparatus comprising the combination with atank adapted to contain a longitudinally flowing body of mineral pulpand having mineral feeding means and pulp discharge means at itsopposite longitudinal ends respectively, of a multiplicity of liquidaerators positioned outside the tank each of which includes a liquid jetdischarge nozzle and a pipe having a constricted bore communicating withthe discharge end of the nozzle, said pipe having at least one air inletopening proximate the discharge end of said nozzle, a multiplicity ofaerated liquid discharge nozzles positioned within said tank proximatethe bottom thereof at points at least an inch inside stantiallyhorizontal plane and over. substantially the'en' tire horizontal area ofthe tank proximate that plane, 'tu'- 3 bular.means extendingtthroughnthewalltof the tank for operatively connecting. each .of saidtaerated'liquid dis.-

chargetlnozzle's to one of said liquid aerators, and a check, valve ineach of said tubular connecting means for prevent? ingthe back flow ofpulp from the tankto the associated liquid aerator;

3."A pneumatic flotation apparatus comprising the combination :with a.tank' ad'apted v .to'.coi1taini a longitudinally fiowin'g body,ofmineral..pulp andlhaving mineral feeding means and pulp dischargemeans at its oppositelongitudi-' nallendstrespectiikely,. of .amultiplicity of liquid aeratorst positionedaoutsidtthe tank .eachofwhich; includes a liq-..

uid jet nozzlewand associated. means ..for drawing .atmos:

phericair intoithe aerator by-vsuctioncreated by the. liqf-V uid jetdischarged fromv the nozzle and anwassociated tubular- -chamberin whichthe drawn-in air is adapted to be thoroughly disseminated throughout.the liquid discharged. from the nozzle; means positioned in proximity tothe.

bottom of the tank for introducing aerated liquid into the tank in asubstantially horiiofitalpl'ane and over substantially the entirehoriz'ontal area of 'the tank-proximate that plane, tubular connectingmeans operatively connecting 1saidtubular chamber to said means- -within-the tank for introducing aerated liquid-;'-and a check-valvei'im eachof i said-tubular connecting means for preventing backflow of pulp fromthe tank to the associated 'liquidaerator.

References Gited-in-the-file of this--patent- UNITED STATES PATENTS864,856: Norris; Sept. 3, 1907 1,159,044"' Klly NOV. 2, 1915 1,167,835NO I' II L ..-L 1311; 11:1916 1,299,059" Taylor ';'.Ap1 1,328,456 ROSS1,720,261 111199, 1929 2,241,337 WOl'k May 6, 1941 2,272,818 Pffb e iF615; 1071942 2,624,657

Anderson Jan. 6, 1953

